Down here in VA, it gets up well into the 90s in the summer with humidity at ridiculous-percent. During those times I haul with the upper doors open in back of the trailer, as the tiny windows in the doors don't seem to provide much airflow.
I feel safer trailering with the upper doors closed completely, but unfortunately we also have the disadvantage of DC traffic, so when we hit gridlock on the beltway, airflow goes from decent to zero. :P
I have the regular T-style latches and have hauled 4+hours on the highway at 60+ mph with the doors open. Haven't had a problem in the 8 years I have had the trailer, except for when the face plate ripped off the side of the trailer due to popped rivets.
That being said, if you can find a fairly recent Trail-Et, check out their latches. They use a lynch pin of sorts that seems much more secure to me than the T-style system. I would love to switch mine out for this system, but cannot find the replacement parts for the life of me.
They also have this system to secure the ramp once it is up and locked into place.
I see that "spring loaded" T-style latch and have to laugh at that tiny little wire. I would be pretty nervous about that holding up.
We were told by a professional hauler (he used a g/n to haul horses to the local emergency vet hospitals, etc) never to leave the top doors open.
He had done his own research, and figured the best ventilation through the trailer came from leaving the side windows and the roof vents open. Driving along drew the air through the side windows and up out of the roof vents, which meant no debris blowing in the horses' eyes, and the warm air was drawn out through the roof vents.
He reckoned that leaving the back doors open meant that exhaust from the towing vehicle was sucked back up over the horses' butts, and made for some discomfort.
I've never put his theories to the test (wish we had access to a wind-tunnel!), but that's how we trailer the horses; doors closed, side-windows and roof-vents open.
You can also rig small 12v revolving fans to ease the horses' comfort, if you can find somewhere safe to mount them.
Living in South Fla where it gets to be 90+ and 90% humidty, it can't be much hotter than anywhere else, so all 3 of my trailers have had fans installed that blow on the horses across their backs. When the trailer is stopped, they are still getting cooled. There is one window on the back door, which I keep open as well (no drop down on this one)
I open the roof vents, slide the side windows open (they are screened), but the drop down windows are closed for safety. I also put a fly mask on my horse to protect his eyes.
I always have my storm doors REMOVED/OFF for 90% of the year. I put them back on for the few months in winter when it rains
But I am a huge believer in stock-sides for trailers for ventilation. So I have a Stock Combo trailer. It's a slant-load with the open slat stock sides, which I have plexi-glass on, in front of the horse's HEADS to protect from debris. But the rest is all open.
I have a ramp as the rear door, and the storm doors close over it - but I simply REMOVE THEM entirely. They are easy to remove on mine. Here it is with the storm doors on and open.....but they are always removed. This was the photo the seller took http://i279.photobucket.com/albums/k...h/PICT0015.jpg
I can't imagine hauling with them just "opened up" unless there was a really really secure way of latching/pinning/securing them to the sides?
Why don't you just remove them for summer/hot weather?
My upper doors are held back with the heavy duty latches with springs. They've held up great even on the freeway.
But the BEST investment I ever made was to install 3 fans in the trailer. They are mounted above the horses' tails and they operate off a battery, so they work even if the truck is not running. They make a huge difference in comfort as they circulate air when we're in traffic. I also have an insulated/lined horse compartment roof, which keeps the horses much cooler in summer.
I found out the hard way. Listen to the manufacturer. NEVER EVER open the top and just latch it back. It needs to be removed, not latched back. Over time, the airodynamics stress the joint and can detach your door. I was lucky, I had a very good latch pin and it was the ONLY thing holding my door onto the trailer. It could have easily flipped and killed someone going through a windshield. I could have been liable for someone killled. NO than you. Just remove them.
Oh Watermark makes a good point about the roof and insulation and fans.
My roof is 100% fiberglass. It is so super cool If you don't have a fiberglass roof, then I'd recommend insulating it, if you haven't already. My friend just bought panels of insulation (foam-looking???) at Home Depot and put them up on the roof herself.
My trailer is a Jamco and has extremely secure latches but I was told that the doors are not designed to withstand highway speed winds and you should not drive on the highways with them open. (Jamco is Canadian so perhaps they don't think so much about Florida/Texas summer travel?)
Interesting about the roof vents- mine can open towards the front so they are either blowing air down into the trailer, or towards the back so air can leave. I always open them front first in the summer so the air blows onto the horse. Hadn't thought of doing it so air can escape up.
The coolest "setting" on my trailer is to open the gooseneck side windows (and all the other ones) -that blows the most air through the trailer.